Hello,
my White Chiffon Rose of Sharon is ailing for about a week or so now, with leaves yellowing out, but otherwise still blooming.
I reached out to your website and we went through possible reasons, like over-watering, pests and so on.
(see my post “My Rose of Sharon is sick”). Nothing seemed to be the case.
But yesterday night i discovered tiny black specs on one of the flowers (see picture – hugely blown up).
Google identified them as Conotelus bug. I drowned them in water. This morning they were on yet another flower.
I checked every other flower on the bush and they were not seen anywhere else.
I was checking flowers and leaves regularly and this is the first time I saw these.
Is it a coincidence or could they have been causing the yellowing of the whole shrub?
If so, how do I fight them?
Thank you
I am impressed with your insect identification! It looks like you have Conotelus bugs, or Obscure Sap Beetles, on your Hibiscus syriacus ‘White Chiffon’. Obscure Sap Beetles are found in Ontario, having migrated up from warmer regions south of the border. They feed on pollen, not nectar as previously thought. They favour flowers with longer throats- that offer them some protection from predators. Hibiscus happen to be heavy pollen producers- so are a perfect host for the Conotelus beetle. Photos can be found here on passion fruit flowers
While these bugs may sometimes chew on other flower parts, leaving holes or damaged petals, they don’t actually cause any permanent damage in the Hibiscus species. Their positive attributes are that they are pollinators and they eat decaying fruit and vegetables and leave the heathy fruit.
This rules Obscure Sap Beetles out as a probable cause for your leaf yellowing issue. I read over my colleagues response to your first post and agree that this is most likely a water issue related to overwatering or poor drainage. I am resending the link Managing Leaf Yellowing
Two key points in the Chlorosis Management (managing leaf yellowing) link is 1. to add organic compost- to improve soil drainage, and 2. not to over fertilize your plant- as this can also cause leaf yellowing, or chlorosis.
Do any other plants in your garden have the same leaf discolouration? If so, a soil test is a good idea. If your soil pH is high your Rose of Sharon will have difficulty accessing the micronutrients it needs to thrive.
I really like the advice from the Morton Arboretum, in the link provided. If you follow the recommendations I think you will see improvements. We are here to help if you continue to have concerns for your Rose of Sharon. Good luck!